It is said that people who belong to the blood group ‘O’ are universal donors, and this unique attribute comes to them genetically. People with the O blood group can give blood to anyone, but receive blood from people who belong to the same group only.
This, however, is not their only unique trait. People with the O blood group are more prone and open to some severe diseases, along with some other powerful characteristics. The best thing about people with O blood is their inexhaustible energy level and their immense focus on whatever task they are doing.

However, the sad bit is that these people are also prone to some scourge diseases, such as:
1) Deficiency of Iodine
2) Dysfunction of Thyroid
3) Low Thyroid Hormone Level
4) Chances of Ulcer
All these hectic and tiring diseases can cause undesired weight gain due to extreme water retention. In some countries like Japan, if a person is being interviewed by his potential employers, he is asked about his blood group. If it is O, he is given a slight edge because these people are considered to be extremely honest and good with their work. Their responsibility of work is what sets them apart from others. However, these people also take a lot of stress and their impulsive nature can be evident. Stress, along with their unhealthy diet, can cause a lot of problems to people who belong to the blood group O.
Source: Blood Type and Personality by syngulate on Rumble
The best thing these people can do is that they avoid taking the stress and relax more. Exercises help in relieving stress and anxiety, which they need to follow. Stress leads to metabolism trouble and causes harmful things like:
1) Resistance of Insulin
2) Thyroid Gland Activity Slows Down

People who belong to this group also have increased levels of stomach acid, compared to all the other blood groups. This causes a lot of stomach issues for them and they need to stay away from all sorts of alcohol and caffeine. Alcohol and Caffeine can be extremely harmful to these people because both of them increase the adrenaline levels of a person.
Since people with blood group O are considered to be rare and unique, it is our moral duty to spread the message with our friends, family, and other loved ones. All these diseases can end up as fatal if proper precautions are not taken.
It is very important for people with O blood group to take care of themselves, especially what they eat. A balanced diet is necessary to rid all these scourge illnesses and live a proper, healthy life.